Sir , How Does It Effect The Cart ? .Is Some Functionality Missing due To this Error

These issues affect session behavior. The short story on sessions is that they are a means to carry data about what a user is doing with the site from one page to the next because without them the site could not behave coherently enough to accomplish work.

A. tell the system to use 'cookies' (little files on the users computer which are then sent back to the server with information it needs to work correctly for the client).B. tell the system to let Abantecart set the "session id" to prevent it from getting confused by outside data.C. tell the system to mark the cookie so that it won't be provided to Javascript components, but ONLY to the HTML components. (roughly).

These help keep your site working correctly and safely.

These can also be configured in either a php configuration file named php.ini (usually) or via an 'htaccess' file in your web root.

If you copy this post to your web host they should be able to help you out now.